I get that error with this IF:

Code:
    IF (UsartFlag = 1)            and _
       (RecvData[0] = UsartRight) and _
       (RecvData[1] = UsartSlave) and _
       (RecvData[2] = Usart0)     and _
       (RecvData[3] = UsartC)     and _
       (RecvData[4] = Usart2)     then
        GOSUB DisplayCOM1
        UsartFlag = 0
    endif

The error goes away if I bump up MaxTvars to 6 in ReEnterPBP.bas.

Was that the proper thing to do? Or will that cause more problems down the road?

(I would think not, but just making sure)